"Delay" number on a Breaker

Liberty44140

I am replacing one of my 30a breakers. It is the breaker at the shore power inlet. It has tripped a few times with the AC, Microwave, and Water Heater all on and while I know that sounds like a lot it only shows 20a at the meter when it trips. Breaker on panel does not trip. Would like to start by replacing the breaker.

QUESTION: What is the "delay" spec on a breaker? The blue sea's offset to my breaker is the same amps, hertz, volts, and trip amps. But my breaker says "72" for the delay and the new blue seas shows "34". Does it matter? Thanks. 

earl1z19

if I had to guess, that might be milliseconds until it trips?

LaRea

I'd get a replacement with the same rating as OEM.  The main breaker is supposed to have a longer delay than any of the sub-circuits.  If the delay on the main is too short, a fault on one of the sub-circuits could trip the main breaker instead of the sub-circuit breaker.  

Handymans342

Breakers are good until they have been cooked over time and then they can’t hold a load. Lol

raybo3

There are 2 types of breakers, time delayed and instantaneous. Time delayed is the most common.....

Liberty44140

Thanks. Sounds like I need to find one with the delay of 72, same as current. Will hunt one down. 

Dutch320

Time delay is very common in circuits that have a motor of some kind, like an AC unit, pump or refrigerator compressor. These types of loads will usually take more amps to start, an inrush of current (amps) will trip an instantaneous breaker. Once the device is running the amp draw levels out. Breakers do go bad or get “weak” usually from repeated tripping. Before you replace the breaker you can amp probe a device at start up on some of the circuits that would be capable of tripping the breaker. A lot of times when a motor is failing it will draw amps in excess of its rated usage. 

Handymans342

Lib, can you post a pic of that breaker?

Liberty44140

This is the best I could get to get specs handy. I did send these numbers to blue seas to see if they have a direct replacement. 

Liberty44140

I probably should have asked this question, but should running a 16k AC unit, Water Heater, and Microwave all at once be ok on a 30A breaker? 

When it blows, the ac compressor is on and active, it is not tripping just on startup. It trips after the microwave runs for 20 seconds or more. The amp meter shows just over 20A when it blows.

Talked to Blue Seas about their option which has the delay of 34 vs my 72 (all other specs match). While they can not 100% say that theirs is fine for my application as they do not know my exact equipment..... they sell 10,000 or more per year of theirs for marine shore power inlets and boards so unless I have something very unique like a gyro, which I dont, theirs should work fine. 

Still working to track down a match. I have an email in to Cruisers parts manager who is usually very responsive. 

LaRea

That load is usually fine on my system.  If I'm also pushing the battery charger full-blast, it might pop the breaker at the pedestal, but not on the boat.  

Liberty44140

Thanks. I didnt want to replace the breaker if those 3 things are actually too much for a 30a dual pole. Chargers and fridges are on a different line so this really is only those three things. I fully understand it could be something other than a bad breaker tripping it, but path of least resistance = start with new breaker

Liberty44140

Got this figured out. Found the exact breaker through Airpax but most distributors didn’t have it or was in back order. Finally found one in stock for $100, before ordering I figured it was worth an email to cruisers and to my luck they had them in stock for $50. Score! Installed and the ac, water heater and microwave will now run without a pop. Bad breaker. 

Handymans342

Great job researching Lib!

Liberty44140

Thanks!